1. Field of the Invention
The present invention relates to a composite substrate for use in a magnetic recording-and-reproducing device, which composite substrate comprises a main plate and a separate sub-plate.
2. Related Art
Magnetic recording-and-reproducing devices and other electronics include printed circuit boards each having a lot of electronic parts to provide electric circuits. Small-sized electric circuits can be efficiently fabricated by installing a large number of electronic parts in a substrate at an increased density, and, advantageously such installation can be automatized.
As a general tendency different electronics have been reduced in size, and accordingly printed circuit boards used have been reduced in size. Downsizing of printed circuit boards meets the requirement for cost reduction, also.
Incidentally, a number of printed circuit boards are cut from a square or rectangular board material of stated size, that is, 1,000 mm by 1,000 mm or 1,000 mm by 1,200 mm.
It is, therefore, required that the number of substrates to be cut from a board material of stated size be so maximized as to make full use of the whole area of the stated size, leaving a minimum total of unused pieces.
FIG. 6 shows a cabinet 1 having a rectangular main plate 2 fitted therein. Likewise, an associated sub-plate 4 is rectangular in shape. These main plates and sub-plates can be cut from a square board material of stated size without allowing any useless pieces to remain for waste, provided that the longitudinal and lateral sizes each of the main and sub-plates are integer multiples of those of the board material. For example, the main plate 2 is 250 mm by 200 mm in respect of a square board material 1,000 mm by 1,000 mm.
As seen from FIG. 6, a deck 3 (broken lines) is laid at a level higher than the main plate 2, and therefore, relatively tall parts cannot be mounted on the main plate 2 except for the non-overlapping area in the main plate 2. Disadvantageously this limits the effective use of the main plate 2 to the non-overlapping area in respect of mounting tall parts.
FIG. 7 shows another conventional cabinet 1 having a relatively small main plate 2, which is so sized that a minimum remaining waste may be left when cutting main plates from the square board material, as for instance follows: the main plate is 250 mm by 166 mm, permitting 24 (=6×4) pieces to be cut from the original square. Such main plate 2 has a shortened vertical size, allowing the overlying deck 3 (broken lines) to extend beyond the lower horizontal side of the main plate 2. This necessitates that one corner of the cabinet 1 cut square to expose the terminals 6a and 6b from the terminal holes, which are made on the rear side of the cabinet 1. Such corner-cut cabinet, however, is less pleasing in appearance.
What is worse is to change the rear, floor and ceiling plates of the cabinet to be in conformity with the corner-cut shape. This requires new molding dies, which cost so much that the amount saved by reducing substrate size (and accordingly increasing the number of substrates to be cut from a single board material) cannot compensate for the amount involved for making such new molding dies.
In view of the above one object of the present invention is to provide a substrate which is so shaped that a possible minimum waste may be left in cutting a square or rectangular board material into as many separate substrates as possible, still allowing each substrate to have a substantial area available to installation of tall parts, standing upright apart from the overlying deck.